Single-molecule Förster Resonance Energy Transfer (smFRET) is a useful technique to probe conformational changes within bio-macromolecules. Here, we introduce how to perform smFRET measurements in solution to investigate RNA remodeling and RNA-protein interactions. In particular, we focus on how the close-to-open transition of an antiterminator hairpin is influenced by the binding of the antitermination protein and the competition by oligonucleotides.